The bench test (1): Dome or eyeball?

The 7728 is a very specialist design that is meant to be installed in suspended or false ceilings and if it gets noticed at all, it looks very like a small spotlight. In theory it could also be wall mounted, though that would depend on the wall, and how easy it would be to accommodate the rear of the assembly and cables, which extend at least 4cm behind the mounting plate.

Inside the 6cm diameter hollow alloy sphere there is a board camera module. The ball is sandwiched between two plates so that when the three fixing screws are slackened, it is able to tilt through almost 180 degrees and pan through 360 degrees. An outer trim bezel is supplied, which hides the mounting plate. This is a bayonet-type fit so there are no exposed screws or fixings and it gives the appearance of being reasonably vandal-proof.

Various camera configurations are available; our sample was a colour model, fitted with an F2.0, 3.6mm lens, in front of a 1/3-inch Sony Hyper HAD CCD image sensor. This has a 752 x 583 pixel array giving a claimed resolution of 480 lines and low light sensitivity of 1 lux. Monochrome camera modules are also available and there is an optional 6mm/F1.8 lens for both types.

There are no external controls or connections and a twin cable emerges from the rear of the camera ball, approximately 28cm in length. This is terminated with an in-line BNC socket carrying the composite video output signal, and a 2.5mm connector for the DC power supply.

The cable on our sample had no anti-strain protection and we suspect that a sharp tug or drop could easily damage the wiring or the small PCB mounted plug that it is attached to. It would be worth putting a cable tie around the cable inside the ball to prevent this happening: this is something the manufacturer should take care of as a matter of urgency.

A 12-volt DC plug-in type mains adaptor is supplied with the outfit, along with mounting plates and spacer, fixing screws and some rudimentary instructions.

Once the sphere is removed from the circular mounting plates it splits apart with a light twist. The actual camera module is made up of two small boards, both heavily populated with surface mounted components. The front board, which has the image sensor and lens, is screwed to a circular plate that ensures it is firmly seated inside the sphere; the front of the lens barrel protrudes through a hole in the front.

The second board is held in place by two multi-pin connectors and when assembled, the whole thing appears to be quite rigid. The quality of construction and finish both appear to be very good; the metal casing and mounting should prove durable. It is not weatherproof though and is designed for interior installation only.

The rearmost of the two camera boards has a four-way miniature DIP-switch, which is used to set the camera's AGC and white balance. The options are eight or 32dB variable gain and auto-tracing white balance or preset switch positions for indoors, outdoors, fluorescent, plus manual set etc. There are no other adjustments, though it is possible to remove the whole module from the front half of the sphere to access the lens and fine-tune the focus.

In most cases installation should be reasonably painless; it is no more difficult to fit than a ceiling panel lighting module, though aligning the camera when it is in position can be quite tricky. That is because a thin rubber O-ring between the mounting plates prevents the sphere from moving smoothly; if you are not careful it seizes completely and the bottom plate has to be removed to free it up. The ball gets surprisingly warm after just a few minutes of operation, probably because it is sealed and there is nowhere for the heat to go. It is probably a good idea to make sure it is sited in a well-ventilated position.

Resolution is not too far off the maker's spec and our sample managed more than 450 lines on our test charts without any problem. Claims for low light performance are possibly just a tad optimistic though, and at very low light levels the picture rapidly descends into a noisy mush.

Nevertheless in good light the picture looks sharp and detailed and if trouble is taken to set the white balance – if it is going to be used in difficult conditions – colours are reasonably accurate.

The auto exposure system responds quickly to changes in light level though it has only limited abilities when it comes to dealing with backlit subjects or scenes or bright lights in the scene area. The camera module is stable and largely immune to mechanical shock.